"It was not normal fire; Crabbe had used a curse of which Harry had no knowledge: As they turned a corner the flames chased them as though they were alive, sentient, intent upon killing them. Now the fire was mutating, forming a gigantic pack of fiery beasts: Flaming serpents, chimaeras, and dragons rose and fell and rose again, and the detritus of centuries on which they were feeding was thrown up in the air into their fanged mouths, tossed high on clawed feet, before being consumed by the inferno."

Contents

Description

Harry casting Aguamenti in a failed attempt to extinguish the cursed fire.

Fiendfyre is a very powerful flame that cannot be extinguished by normal water but is very difficult for the caster to control. The blaze is so potent that Fiendfyre is one of the very few substances that are capable of destroying a Horcrux.

It initially appears as a "roaring, billowing noise" and gives its victims only a moment's warning. Its flames are of abnormal size and take the shape of fire-breathing monsters and beasts, such as serpents, chimaeras, dragons, and raptors, continuously mutating. It appears to have enough consciousness to actually follow its intended victims. The fire will pursue nearby lifeforms as if it were alive itself, sentient, even the one who conjured it if they lack control. The fire will also pursue anything it can burn for more fuel and seems to incinerate anything through mere contact.[1]

Inexperienced casters will be able to conjure it, but will have virtually no control over the flames once they are unleashed, which would make the flames a potential deadly backfire.[1] It seems like the flames feed off the caster's emotions and when they are insufficient in controlling such emotions while casting the curse, it becomes the reason for the backfire; the caster themselves would become a target of the indiscriminate inferno, which would devour everything in the vicinity, including the one who created it.[2]Hermione Granger, a very skilled and intelligent witch, had her own doubts of being able to control such dangerous flames, further indicating its difficulty.[1] This being said, it seems that only the most experienced Dark Wizards (like Lord Voldemort)[3] would be able to control it and manipulate it to great effect.

It was mentioned by Ron Weasley that Vincent Crabbe was not paying attention in class when they were taught how to stop Fiendfyre.[1] Though this is mostly Ron being sarcastic, it is possible that there is a counter-spell to cease the otherwise seemingly unstoppable flames, if controlled by a skilled wizard, or that it could even burn itself out naturally. Fiendfyre (or any other magical fire) that is allowed to burn unchecked for too long they can produce an Ashwinder; it is said that Ashwinders are born from the embers of a dying fire, so this is another indication that Fiendfyre can die out in time.

When the diadem, having been exposed to the flames before its recovery, broke apart in Harry's hands upon their escape, Hermione realised it was Fiendfyre they had escaped from. She had known that it was capable of destroying Horcruxes, but claimed it was far too dangerous for her to attempt to use.[1]

Etymology

The word "Fiendfyre" was probably derived from "fiend" (meaning an evil spirit or demon or "The Devil", a representation of the flame's cursed properties and taking form of dark creatures) and fire.

"Fyre" comes from the Old English word "fyr", which in turn is for "fire". Directly, "fyre" is just a single-letter corruption of "fire". Fire is the main effect of the curse.

Behind the scenes

Though the only confirmed use of this spell is by Crabbe in the Room of Requirement,[1][2] there are numerous instances of living fire shown in the films that resembles Fiendfyre, either being it or a variant. These include:

In Harry Potter and the Deathly Hallows: Part 2, Gregory Goyle uses Fiendfyre and dies instead of Crabbe. This is due to the fact that Crabbe has been cut from the film. Unlike Crabbe's failing control over the flames and unseen death, Goyle died by falling into the inferno after grabbing a loose chair from climbing a mountain of old stuff. Also, Goyle's lack of control is depicted as him having trouble stopping the flames from coming out of his wand once he cast the curse.[2]

In the film adaption, Fiendfyre was not used to completely destroy Rowena Ravenclaw's Diadem. Instead, Harry stabbed it with the Serpent of Slytherin's fang to damage it, and then Ron kicked it into the Fiendfyre to finish the job. This led Voldemort's mangled soul to possess the flames briefly and screaming in pain before it was destroyed.[2]